Here are the data structures with brief descriptions:

CAllGlobals
CARGBUFFER
Cbit_field
CBrAcKeTiNdEx
CBracketInfo
CBrAcKeTiNfO
CbufIPstruct
CC_const
CCbUf
CChAnNeL
CCOST
CCSEEq
CCSEHash
Cdbase
CDICTIONARY
CDICTIONARY_ELEMENT
CDiStRiBuTe
Cdollar_buf
CDoLlArS
CDoLoOp
CDuBiOuS
CEEdge
CEGraph
CENode
CExPrEsSiOn
CFaCdOlLaR
Cfactorized_poly
CFiLe
CFiLeDaTa
CFiLeInDeX
CFixedGlobals
Cfixedset
CFUN_INFO
CFuNcTiOn
Cgcd_heuristic_failed
CHANDLERS
CInDeX
Cindexblock
CInDeXeNtRy
Ciniinfo
CINSIDEINFO
CKEYWORD
CKEYWORDV
CLIST
ClongMultiStruct
CM_const
CMGraph
CMiNmAx
CMNode
CMNodeClass
CMODNUM
CMoDoPtDoLlArS
Cmonomial_larger
CN_const
Cnameblock
CNaMeNode
CNaMeTree
CNeStInG
Cnode
CNoDe
CNodeEq
CNodeHash
CO_const
Cobjects
Coptimization
COPTIMIZE
COPTIMIZERESULT
CP_const
CParallelVars
CPaRtI
CPeRmUtE
CPeRmUtEp
CPF_BUFFER
Cpoly
CPOLYMOD
CPoSiTiOn
CPRELOAD
CpReVaR
CPROCEDURE
CR_const
CReNuMbEr
CS_const
CSeTs
CSETUPPARAMETERS
CSHvariables
CsOrT
CSpecTatoR
CStOrEcAcHe
CSTOREHEADER
CStreaM
CSuBbUf
CSWITCH
CSWITCHTABLE
CSyMbOl
CT_const
CTaBlEbAsE
CTaBlEbAsEsUbInDeX
CTaBlEs
CToPoTyPe
CTrAcEn
CTrAcEs
Ctree
Ctree_node
CVaRrEnUm
CVeCtOr
CX_const